A 32-year-old man was admitted after bone marrow transplantation because of hematochezia. He had history of chronic graft-versus-host disease (GVHD) of the skin and the liver, and cytomegaloviral pneumonia. Barium enema and colonoscopy showed multiple colon ulcers in the ascending and transverse colon. This feature is very rare in chronic GVHD and resembles the feature in autoimmune disease such as periarteritis nodosa. Thus, this ulceration is thought to be caused by vasculitis due to an autoimmune reaction in chronic GVHD.